Slow down the work navbar does, and cancel updating it when receiving a high volume of user events

src/EditorFeatures/Core/NavigationBar/NavigationBarController.cs

@@ -61,10 +61,9 @@ internal partial class NavigationBarController : IDisposable
 
     /// <summary>
     /// Queue to batch up work to do to compute the current model.  Used so we can batch up a lot of events and only
-    /// compute the model once for every batch.  The <c>bool</c> type parameter isn't used, but is provided as this
-    /// type is generic.
+    /// compute the model once for every batch.
     /// </summary>
-    private readonly AsyncBatchingWorkQueue<bool, NavigationBarModel?> _computeModelQueue;
+    private readonly AsyncBatchingWorkQueue<VoidResult, NavigationBarModel?> _computeModelQueue;
 
     /// <summary>
     /// Queue to batch up work to do to determine the selected item.  Used so we can batch up a lot of events and
@@ -93,15 +92,15 @@ public NavigationBarController(
         _uiThreadOperationExecutor = uiThreadOperationExecutor;
         _asyncListener = asyncListener;
 
-        _computeModelQueue = new AsyncBatchingWorkQueue<bool, NavigationBarModel?>(
+        _computeModelQueue = new AsyncBatchingWorkQueue<VoidResult, NavigationBarModel?>(
             DelayTimeSpan.Short,
             ComputeModelAndSelectItemAsync,
-            EqualityComparer<bool>.Default,
+            EqualityComparer<VoidResult>.Default,
             asyncListener,
             _cancellationTokenSource.Token);
 
         _selectItemQueue = new AsyncBatchingWorkQueue(
-            DelayTimeSpan.NearImmediate,
+            DelayTimeSpan.Short,
             SelectItemAsync,
             asyncListener,
             _cancellationTokenSource.Token);
@@ -195,8 +194,7 @@ private void StartModelUpdateAndSelectedItemUpdateTasks()
         if (_disconnected)
             return;
 
-        // 'true' value is unused.  this just signals to the queue that we have work to do.
-        _computeModelQueue.AddWork(true);
+        _computeModelQueue.AddWork(default(VoidResult));
     }
 
     private void OnCaretMovedOrActiveViewChanged(object? sender, EventArgs e)

src/EditorFeatures/Core/NavigationBar/NavigationBarController_ModelComputation.cs

@@ -14,6 +14,7 @@
 using Microsoft.CodeAnalysis.Text;
 using Microsoft.CodeAnalysis.Workspaces;
 using Microsoft.VisualStudio.Threading;
+using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.Editor.Implementation.NavigationBar;
 
@@ -22,7 +23,7 @@ internal partial class NavigationBarController
     /// <summary>
     /// Starts a new task to compute the model based on the current text.
     /// </summary>
-    private async ValueTask<NavigationBarModel?> ComputeModelAndSelectItemAsync(ImmutableSegmentedList<bool> unused, CancellationToken cancellationToken)
+    private async ValueTask<NavigationBarModel?> ComputeModelAndSelectItemAsync(ImmutableSegmentedList<VoidResult> _, CancellationToken cancellationToken)
     {
         // Jump back to the UI thread to determine what snapshot the user is processing.
         await _threadingContext.JoinableTaskFactory.SwitchToMainThreadAsync(cancellationToken).NoThrowAwaitable();
@@ -98,8 +99,8 @@ await _visibilityTracker.DelayWhileNonVisibleAsync(
     /// </summary>
     private void StartSelectedItemUpdateTask()
     {
-        // 'true' value is unused.  this just signals to the queue that we have work to do.
-        _selectItemQueue.AddWork();
+        // Cancel any in flight work.  This way we don't update until a short lull after the last user event we received.
+        _selectItemQueue.AddWork(cancelExistingWork: true);
     }
 
     private async ValueTask SelectItemAsync(CancellationToken cancellationToken)